1. Technical Field
This disclosure relates to a liquid ejection head and an image forming apparatus including the liquid ejection head.
2. Description of the Related Art
Image forming apparatuses are used as printers, facsimile machines, copiers, plotters, or multi-functional devices having, e.g., two or more of the foregoing capabilities. As one type of image forming apparatuses employing a liquid-ejection recording method, for example, inkjet recording apparatuses are known that use a recording head (liquid ejection head or liquid-droplet ejection head) for ejecting droplets of liquid (e.g., ink).
Such a liquid ejection head may have a common liquid chamber and individual liquid chambers communicated with nozzles and eject liquid droplets from the nozzles by increasing internal pressure of the individual liquid chambers (also referred to as pressure chambers). Such increased pressure while ejecting liquid droplets from the nozzles, is transmitted to the common liquid chamber. When such pressure is transmitted back to the individual liquid chambers, the pressure in the individual liquid chambers may fluctuate to unexpected values. As a result, liquid droplets may not be ejected at a desired droplet amount and/or speed, thus causing ejection failure. In particular, when a plurality of individual liquid chambers is simultaneously pressurized to eject liquid droplets, a relatively high pressure may be transmitted from the common liquid chamber to the individual liquid chambers, thus causing ejection failure. Such fluctuations in pressure transmitted to the common liquid chamber may be transmitted to adjacent individual liquid chambers and affect liquid in the individual liquid chambers, thus causing unstable liquid ejection or unintentional leak or ejection of liquid droplets from nozzles. As a result, high-quality image output may be hampered.
Hence, for example, JP-2009-083243-A proposes a liquid ejection head having a common liquid chamber plate and a damper plate. The common liquid chamber plate includes a common liquid chamber hole penetrating through the plate and having an elongated shape along an array direction of the pressure chambers to form a common liquid chamber to lead liquid from a liquid supply source to a plurality of pressure chambers. The damper plate has a damper wall to buffer fluctuations in pressure in the common liquid chamber. The damper wall forms a wall portion in which a face of the damper plate opposite a face opposing the common chamber plate is partially recessed and has a relatively small plate thickness at the common liquid chamber side in such recessed area. In plan view, the damper wall has a contour greater than that of the common liquid chamber hole. A peripheral edge of the damper wall forms a thin plate portion of a smaller thickness than a central portion of the damper wall. In plan view, the common liquid chamber plate and the damper plate are adhered each other with the thin plate portion of the damper plate placed outside the common liquid chamber hole.
Alternatively, JP-2006-198903-A proposes an inkjet head having a flexible plate in which a plurality of nozzles is bored. The flexible plate has a portion serving as a wall of a common ink chamber and an attenuation portion more deformable than other portions. The attenuation portion is formed along and near the periphery of the common ink chamber. The wall includes a damper portion for absorbing pressure waves of ink transmitted from pressure chambers to the common ink chamber.
A thinner damper, as shown in JP-2009-083243-A and JP-2006-198903-A, is more likely to absorb vibration. However, the inventor has recognized that such a thinner damper is more likely to be damaged at a starting portion of deformation. In particular, when initial liquid filling is performed on the inkjet head, liquid is sucked from the recording head or supplied to the recording head by pressurizing the head. As a result, the damper may be excessively deformed, which becomes more likely to be damaged.